Lubricants containing charge transfer complexes of iodine and aromatic compounds



Jan. 11, 1966 R. w. ROBERTS ETAL 3,228,880

LUBRICANTS CONTAINING CHARGE TRANSFER COMPLEXES OF IODINE AND AROMATIC COMPOUNDS Flled June 12, 1962 lm/emors H/c/zard l l/ Robe/f5 fioberf 5. Owe/7s, W ,1

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United States Patent 3,228,880 LUBRICANTS CGNTAINING CHARGE TRANSFER COMPLEXES OF IODINE AND AROMATIC COM- POUNDS Richard W. Roberts, Schenectady, and Robert S. Owens, Latham, N.Y., assignors to General Electric Company, a corporation of New York Filed June 12, 1962, Ser. No. 201,952 Claims. (Cl. 25251) The present invention relates to improved lubricants and uses of these materials as lubricants for various contacting surfaces, at least one of which is at least 50% by weight titanium. More particularly, the invention relates to a new class of lubricants which are charge transfer complexes of iodine and aromatic compounds. These lubricants have been found to be especially useful in those cases where new metal surfaces are being created or where high wear is a problem particularly in the case of boundary lubrication. These lubricants may be used either alone or as additives in combination with other well known hydrocarbon lubricants having the desired lubricating viscosity, such as mineral oils, in the form of solutions, or with thickening agents to form greases, etc.

Attempts have been made in the past to effect lubrication of titanium and its alloys. Thus, it has been desired to effect lubrication of relatively moving surfaces in which one of the surfaces is a metal composition containing at least 50% by weight titanium, generally known :as titanium-based metals, e.g., pure titanium, commercially pure titanium, alloys of titanium, etc. The lubrication of such titanium surfaces is especially difficult in cases where extreme pressure conditions exist requiring lubrication under boundary conditions, i.e., actual, solid-to-solid contact, for instance, as may be found in a bearing before a hydrodynamic film of a lubricant is created, or where new solid surfaces are being generated, for example, in shaping by drawing through a die, in cutting, for example, in lathe or punch-press, in shaping, for example, by stamping, drawing, extrusion, spinning, cold rolling, in polishing, for example, by lapping, burnishing, slowly moving sliding parts in contact with each other, etc. For convenience, this type of lubrication is hereinafter referred to as boundary lubrication. Under such conditions, it has been found that titanium and its alloys are lubricated with great difficulty due to the fact that under extreme pressure conditions of boundary lubrication the titanium surface tends to score, gall or seize, even when great care is exercised. To the best of our knowledge, no previous lubricant has been known which completely satisfies the requirements of boundary lubrication of titanium metal compositions containing at least 50% by weight titanium.

It has been proposed for example to electroplate or otherwise coat titanitun or its alloys with a hard metal or sacrificial coating which can be readily lubricated. However, since these coatings are subject to wear, this protective lubricating action is soon lost and in addition is expensive and therefore not a satisfactory solution to the problem. It was also found that iodine would react with titanium metal, which has been outgassed at high temperature, in a vacuum, to form a titanium diiodide coating which possessed lubricating properties, but unfortunately, the titanium iodide coating cannot be used in air or moist atmospheres since moisture reacts to form titani- See um oxide and hydrogen iodide. Of all the liquids investigated, methylene diiodide a halohydrocarbon oil, s-tetrabromoethane and 1,2,3-tribromopropane have been found to be good lubricants for titanium, but unfortunately, in addition to being not readily available and expensive, it has been found that they cannot be used as additives to other lubricants to provide an economically feasible lubricant for titanium, since dilution causes the coefiicient of friction to rise to an impractically high value.

Unexpectedly, we have found that charge transfer complexes of iodine and aromatic compounds can be used as lubricants between two solid surfaces which move relative to each other, at least one of which is at least 50% titanium, even under high pressure conditions, or may be used as additives to other well known lubricants to impart improved boundary lubricating characteristics to such lubricants as for example those mentioned above, examples of which are mineral oils of lubricating viscosity, lubricating greases, etc. When these iodine charge transfer com plexes are employed in lubricating the titanium surface or surfaces, it is found that the coeflicient of friction is greatly reduced and the tendency to gall or seize, particularly under boundary lubricating conditions, is materially reduced and in many instances is completely eliminated. Furthermore, it was found that in addition to including lubricating characteritics of these iodine charge transfer complexes, the act of one surface moving across another surface in the presence of these iodine charge transfer complexes imparts a high polish to the titanium surface in many applications, thereby still further increasing the ease with which our lubricating compositions can contribute to the lubricating act.

'The fact that our iodine charge transfer complexes may be used as lubricants for these various classes of materials and are particularly useful as lubricants under a Wide variety of conditions for two solid surfaces moving relative to each other, where at least one of the surfaces is either titanium or an alloy of titanium, was entirely unexpected and in no way could have been predicted. It is known that a solution of iodine, e.g., in alcohol, is not a lubricant for titanium. The prior art has been of the impression that the usual lubricants and the usual lubricating materials and techniques were not effective lubricants under many conditions for relatively moving surfaces in which one of the surfaces was titanium or one of its many alloys. This is due to the fact that titanium and many of its alloys have well known characteristics of readily galling and seizing, and when the usual lubricants, even extreme pressure lubricants containing additives to increase the load bearing characteristics of the lubricant are used for lubricating such materials, undesirable wear, galling and ultimate seizure of the relatively moving parts occurs. This is particularly borne out by a recent article by Ernest Rabinowicz, Wear, Scientific American, February, 1962, page 131, where the author points out that titanium cannot be effectively lubricated by any known substance and, therefore, no one has yet made a sliding surface of titanium, although the metal has found many static applications.

Our new lubricants are charge transfer complexes of iodine and aromatic compounds. When iodine is dissolved in certain organic liquids, it forms a charge transfer complex. The organic compound is an electron donor giving up an electron to the iodine so that the organic compound becomes positively charged and, the iodine negatively charged, resulting in what has become known as a charge transfer complex of iodine and the orgaruc compound. Charge transfer complexes of iodine with solid organic compounds are also possible and can be made either from the molten organic compound or from a solution of the solid organic compound in a solvent which can either be one which does or does not by itself form a charge transfer complex with iodine. These charge transfer complexes of iodine with organic compounds are well known and are described for example in such articles as Structures of Complexes Formed by Halogen Molecules with Aromatic and with Oxygenated Solvents, by Robert S. Mulliken, J. Am. Chem. Soc., 72, 600-608 (1950); Energetics of Molecular Complexes, by S. P. McGlynn, Chem. Rev. 58, 1113-1156 (1958); The Theory of Charge-Transfer Spectra, by I. N. Murell, Quart. Rev., 15, 191-206 (1961), and various references cited in each; etc. The particular iodine charge transfer complexes which we have found are lubricants for titanium and its alloys are those formed between iodine and aromatic compounds. These charge transfer complexes are readily identified by the fact that they have a very strong ultraviolet absorption, near 3,000 lambda, and a visible absorption near 5,000 lambda, which is not found for iodine in a solvent which does not form the charge transfer complex, nor for the aromatic molecules themselves.

As far as we can determine, all aromatic compounds, both substituted and unsubstituted, are capable of forming charge transfer complexes with iodine. This includes the completely aromatic hydrocarbons such as benzene, naphthalene, diphenyl, anthracene, phenanthrene, fluoranthene, pyrene, chrysene, naphthacene, etc., including those aromatic hydrocarbons having aliphatic substituents, for example, toluene, xylene, mesitylene, hexamethylbenzene, ethylbenzene, propylbenzene, butylbenzene, octylbenzene, the methyl naphthalenes, acenaphthene, fiuorene, indene, etc., as well as the aromatic heterocyclic compounds, for example, thiophene, pyridine, the picolines, quinoline, isoquinoline, quinaldine, indole, acridine, carbazole diphenylene oxide, etc., including the above compounds where one or more of the hydrogen atoms are substituted by, for example, a halogen, primary, secondary and tertiary amino, sulfamoyl, sulfo, nitro, ester groups, for example, carboalkoxy, carboaroxy, sulfo- :alkoxy, etc., carboxyl, carbonyl, sulfonyl, for example, sulfonic esters hydroxyl, ethers, etc. For ordinary applications, we prefer to use hydrophobic aromatic compounds, i.e., aromatic compounds, that are free of hydrolyzable and ionizable substituents, since such groups in the presence of water, if it is introduced into the lubricant, tend to cause pitting and corrosion of the metallic surfaces. However, there are many applications for lubricants where water is excluded where such substituents would not present any difficulties in the use of such aromatic compounds as lubricants in the form of a charge transfer complex with iodine. Other aromatic compounds which form charge transfer complexes with iodine are disclosed, for example, in the above references and the literature references cited therein, as well as in other publications.

These charge transfer complexes which are liquids at the ambient temperature of application can be used by themselves as lubricants for titanium and its alloys and, in addition, may be used in solution as may the iodine charge transfer complexes of aromatic compounds which are normally solid. The solvents used to dissolve the charge transfer complexes may be merely diluents or they may also form charge transfer complexes with iodine or they may be hydrocarbon oils having a lubricating viscosity. Preferably, if a solvent is used, it is a hydrocarbon oil, for example, those derived from mineral oils having lubricating viscosity. Such materials may be used alone or with thickeners to form greases or other additives such as viscosity stabilizers, pour point depressants, high pressure additives, etc.

Because of the ready availability of the raw materials, and because they are liquids at room temperature, we prefer to use aromatic compounds of the benzene series for forming the iodine charge transfer complexes. If the charge transfer complexes are to be used alone, the particular aromatic compound is so chosen as to have a suitable boiling point so that it does not evaporate under the conditions of use at a rate faster than can be tolerated for the specific application. Mixtures of one or more aromatic compounds which form an iodine charge transfer complex may be used to form lubricants having specific tailor-made properties and these charge transfer complexes may likewise be used alone or in a solvent which does not form a charge transfer complex.

When one solid surface moves relative to another surface with a lubricant between the two surfaces, there may be a complete film of lubricant separating the two surfaces or there may be varying degrees of solid-to-solid contact. The former condition exists under hydrodynamic lubrication while the latter condition is characteristic of boundary lubrication. Complete hydrodynamic lubrication may be obtained under certain ideal conditions found in bearings, but it is influenced by such factors as design of the two solid surfaces, load on the surfaces, and the relative speed of the one part to the other. However, even under these conditions, boundary lubricating problems are encountered during stopping and starting operations, and from a practical standpoint, perfect hydrodynamic lubrication is approached rather than attained. Therefore, the ability to improve boundary lubrication is to be greatly desired.

Our compositions improve the lubricating of two solid surfaces moving relative to each other, when at least one of the surf-aces is a metal which is at least 50% titanium. The other surface may be a metal used for fabricating structural shapes, e.g., iron, molybdenum, silver, copper, beryllium, tungsten, magnesium, titanium, Zirconium, chromium, nickel, cobalt, aluminum, tin, etc., and various metal compositions, for example, alloys, of which typical examples are steels brasses, the various alloys of magnesium, cobalt, zinc, zirconium, beryllium, aluminum, iron (e.g., stainless steels) etc. The other surface may likewise be wood, molded synthetic resins, laminates, etc., or a special compound composition such as porous metal, graphite, graphite-impregnated metal, softening alloys, e.g., babbitts, etc., or very hard compositions, e.g., metal carbides, nitrides, etc.

Nominally, in the design of equipment where one solid surface moves relative to another, both solid surfaces are the same material if wear is to be equal on both parts, or one is made of a material softer than the other when the wear is to be essentially all in the softer part. This is usually done when one part is easier to replace than the other, or one part is being cut or shaped by the other.

Although we do not wish to be bound by theory, it is believed that these iodine charge transfer complexes of an aromatic compound are capable of lubricating titanium and its alloys because the aromatic compound activates the iodine so that it is capable of reacting in some way with the titanium to produce a lubricating film which substantially reduces the coeflicient of friction and greatly reduces or eliminates the tendency of the titanium to gall. The aromatic compound serves a secondary function of also protecting this layer from atmospheric attack which would destroy it. Therefore, the amount of iodine present as the charge transfer complex may be only present in an amount sufiicient to form this layer on the rubbing surfaces of the titanium, or its alloys, and provide sufficient iodine'to re-form this layer if the application involves a use which would tend to create new surfaces as the old surface is worn away. We have found that as little as 0.1% by weight of iodine based on the entire weight of the lubricating composition will be satisfactory but in those applications where the lubricant is to be used for extremely long periods of time, the amount of iodine is preferably at least 1%, up to the concentration which represents the saturation concentration of the iodine in the composition. Since the ability of the aromatic compound to dissolve iodine varies depending upon the particular aromatic compound chosen, if an extremely high concentration of iodine is desired, the aromatic compound should be chosen which is capable of dissolving and forming the charge transfer complex of a desired amount of iodine. Likewise, if the lubricant is to be used in an atmosphere containing water vapor, the particular aromatic compound should be chosen to have hydrophobic characteristics to render the maximum protection to protect the lubricating film formed by the iodine. As will be obvious to those skilled in the art of lubrication, the aromatic compound used to form the charge transfer complex with iodine should be one which will be stable under the conditions to which it will be subjected as a component of the lubricant, i.e., will not spontaneously decompose or be reactive with the surfaces with which it will be in contact.

Our belief that the iodine must be in an activated form as provided by the charge transfer complex is based on the fact that when iodine is dissolved in an organic compound which does not form a charge transfer complex, even though the organic compound is a lubricant having lubricating viscosity, for example, mineral oil, such a composition is entirely unsuitable for the lubrication of titanium and its alloys. It is therefore evident that the ability to lubricate titanium and its alloys is not provided by the mere presence of iodine, but can only be provided by iodine in the form of a charge transfer complex with an aromatic compound. This discovery permits the use of a Wide variety of titanium compositions for the first time in the fabrication of bearings and like surfaces, since, as far as we are aware, prior to our invention, no way was known to prevent galling and seizing of bearing surfaces made of many of these materials, except by the use of indirect methods or by the use of very expensive and not readily available materials. Our

iodine charge transfer complexes or mixtures thereof may i also be used for applications in which titanium or its alloys are shaped, for example, by drawing, spinning, extrusion, and the like.

Typical examples of the various titanium compositions that may be lubricated by our iodine charge transfer complexes are those disclosed on pages 1147-1156 of Metals Handbook, vol. 1, Properties and Selection of Metals, American Society for Metals, Novelty, Ohio, Eighth Edition, 1961, for example, a high purity titanium, commonly known as unalloyed titanium, available both in purities of 99.2% and 99.0% titanium, and the titanium alloys with other metals, for example, aluminum, tin, iron, chromium, molybdenum, manganese, vanadium, etc., as are more fully described on pages 1153-1156 of the above reference.

Typical of the mineral or hydrocarbon oils of lubricating viscosity are the hydrocarbon lubricants obtained from petroleum. These products normally have viscosities in the range of 25 to 10,000 Saybolt Universal seconds (S.U.S.) and may be a single hydrocarbon, but usually are a mixture of hydrocarbons.

Compositions of our invention vary from liquid to solid materials. The solids when dissolved in lubricating oils are capable of producing fluid and greases having lubricating properties depending on the composition and concentration.

To aid in obtaining the grease-like consistency desired for lubricating greases, non-abrasive fillers such as silica gel, carbon black, diatomaceous earth, molybdenum sulfide, tin sulfide, graphite, etc., may be added, or soaps or other materials may be incorporated to produce gel structure. Likewise, mixtures of these materials may be added to produce useful compositions. Particularly useful soaps are the metallic soaps, such as the alkaline and alkaline earth soaps of the fatty acids, but other soaps may also be used, for example, zinc, tin, lead, copper, etc., soaps of the fatty acids. Particularly desirable grease compositions may be made from lithium stearate or lithium hydroxy stearate. These grease compositions may be made by any of the well known methods, for example, as disclosed in US. Patents 2,450,221, Ashburn et al., 2,450,- 222, Ashburn et al., and 2,260,625, Tisler. Satisfactory greases may be made by merely mixing the iodine charge transfer complex, a lubricating oil, and a soap at room temperature. In addition, pour depressants, stabilizers, inhibitors, and the like, may be added to our compositions, if desired.

In order that those skilled in the art may better understand how our invention may be practiced, the following examples are given by way of illustration and not by way of limitation. In all of the examples, the percentages are by weight.

In order to determine the ability of the charge transfer complexes of iodine and an aromatic compound to satisfactorily lubricate two surfaces, one moving relative to the other, the following tests were carried out using a modified four-ball wear test machine described, for example, in an article by R. G. Larson entitled, Study of Lubricating Using Four-Ball Type Machine, Lubrication Engineering, 1, page 35, August, 1945. This machine was modified by replacing the four balls and their holder with a cup and washer as shown in the drawing. Rider 1 made of one of the metals to be investigated is cupshaped and is rotated at preselected speeds against a stationary test washer 2 made of the same or different metal to be tested by means of motor driven shaft 3 to which rider 1 is attached by machine bolts 4 and 4. Washer 2 is rigidly fastened by means of machine bolt 7 to a base member 5 which is restricted from rotation with respect to chamber 6. A reservoir of lubricant 8 under test is maintained around the test pieces. A heater (not shown) is provided in the base of chamber 6 to permit operation at various temperatures. Chamber 6 rides on a series of ball bearings, one of which is shown as 9 which ride upon member 10 which forms the uppermost portion of plunger 11 which is connected to a hydraulic system (not shown) to permit various loadings to be established between the two test samples 1 and 2. When rider 1 is rotated against test washer Z by means of clockwise rotation of shaft 3, chamber 6 will rotate upon member 10 due to the frictional force existing between members 1 and 2. The force required to prevent such rotation is measured by a strain bridge attached to arm 12. This modification permits the coefficient of friction to be calculated and examination of rides 1 and 2 permits the evaluation of the amount and type of wear produced. It is desirable to have the lowest surface of rider 1 in parallel contact with the upper surface of washer 2. This can be obtained either by machining the rider and washer to close tolerances or more conveniently by inserting a resilient pad (not shown) between the base member 5 and the top surface of the heater in the base of chamber 6. Since this pad must be resistant to oil and heat, it is conveniently made of silicone rubber. This pad not only permits the washer 2 and base member 5 to self-adjust so that the top surface of washer 2 will be in parallel contact with the lower surface of rider 1, but also prevents base member 5 from rotating on the face of the heater without fastening.

Using this apparatus, the results given in the following examples were obtained. The rider with a flat annular area of 0.396 square inch was rotated under a 10 kilogram load at 0.88 r.p.m. (surface speed of 0.0461 inch per second) against the test washer. These conditions represent operation in the boundary friction region, the

EXAMPLE 1 In this test both the washer and the rider were high purity titanium. Table I shows the lubricant used in each of the runs and the results obtained.

In the appended claims we use the term solid as' an adjective in its broad sense to differentiate between solids, liquids, and gases. The term solid part includes within its meaning those solid bodies which are hollow, honeycombed, porous, etc., bodies which have a solid surface.

The above examples have illustrated many of our compositions which may be utilized as lubricants. Equally good results were obtained by utilization of other compositions falling within the terminology of a charge transfer complex of iodine and an aromatic compound. The examples have also illustrated many of the ways that our compositions may be mixed with other materials to provide outstanding lubricants. Other modifications and variations will be readily apparent to those skilled in the art, and are included within the meaning of the appended claims.

The n-butyl benzene forms a charge transfer complex with the iodine and is a deeply-colored solution with broad absorption band centered at 5,000 Angstroms. As is evident from the results in Table I, neither the hydrocarbon oil, the hydrocarbon oil plus iodine, nor butyl benzene alone was satisfactory as lubricants for the titanium rotating on titanium, while the charge transfer complex formed between iodine and n-butyl benzene was satisfactory.

EXAMPLE 2 In this test, the rider was made of cold rolled steel and the washer of titanium. The results with various lubricants are shown in Table II.

Table 11 Time, Max. Wear Coeff cient Lubricant Minutes Track Depth of Friction (mils) SAE 10 Spindle Oil 190 2 0. 54 0. 68 n-Butyl benzgneflu F f 140 0. 9 0. 47-0. 68 91 n-But l enzene iz dineui .f 290 0. 4 0. 19-0. 27 45% n-Butyl bseiizignle), 5% d1 d' e, 50 s in e iiil m p 230 0. 8 0. 19-0. 27 Benzene 270 O. 7 0. 4-0. 6 90% benzene, 4% icy dinei 160 0. 1 0. 1-0. 17 24.57 benzene, 1.5 to ine,

747'; SAE 10 spnile oily. 120 0. 5 0.17-0.27 27 methylene i i e, 98 o SAE 10 spindle iifl n 120 1. 0. 34-0. 68 98.8 di hen let er, .2

l0 i 11%R- Y 200 01 0. 14-0. 2 49.4% diphenysl 0.0%d1

' d 50 t s in e oil f i i H 350 0.8 (only one 0.17-0.28

groove) 96.7% anisole, 3.3% iodine 310 0. 1 0. 14-0. 2 48.4% anisole, 1.6% i0dine, 50%

SAE spindle 011 370 0. 5 0. 17-0. 22 97.4% m-xylene, 2.0g, iodine- 1200 0. 4 0.17-0.25 48.77 m-xylene, 1.3 iodine,

507i SAE 10 spindge oili 330 0. 2 0. 2-0. 24 4 naphthalene, 0.5 ie ine 55.5% SAE 10 spind le oil. 130 0. 8 0.17-0.27 99% thiophenol, 1% i0dine 5 0. 1 0.3-0.4 99% nitrobenzene, 1% iodine 110 0. 1 0. 24-0. 47 99% pyridine, 1% iodine 70 0. 1 0. 23-0. 4 99% ethyl benzoate, 1% iodine.-- 390 0. 1 0. 19-0. 25 99% 0l1l01013fi11%6116,1 1% ip gina" 170 0. 1 0. -0. 22

9 2,6-d'et -ani ine,

All of the aromatic compounds shown in Table 11 form charge transfer complexes with the iodine with whlch they are used.

What we claim as new and desire to secure by Letters Patent of the United States is: I A lubricant comprising a hydrocarbon oil of lubricating viscosity containing dissolved therein a charge transfer complex of iodine and an aromatic compound stable under the conditions it will be subjected to as a component of the lubricant, there being at least 0.1% by Weight iodine, in the form of the complex, in the lubricant.

2. A lubricant comprising a hydrocarbon oil of lubricating viscosity containing dissolved therein a charge transfer complex of iodine and aromatic hydrocarbon, there being at least 0.1% by weight iodine, in the form of the complex, in the lubricant.

3. A lubricant comprising a hydrocarbon oil of lubricating viscosity containing dissolved therein a charge transfer complex of iodine and an alkyl-substituted aromatic hydrocarbon, there being at least 0.1% by weight iodine, in the form of the complex, in the lubricant.

4. A lubricant comprising a hydrocarbon oil of lubricating viscosity containing dissolved therein a charge transfer complex of iodine and a halogenated aromatic hydrocarbon, there being at least 0.1% by weight iodine, in the form of the complex, in the lubricant.

5. A lubricant comprising a hydrocarbon oil of lubricating viscosity containing dissolved therein a charge transfer complex of iodine and a hydrocarbonoxy-substitued aromatic hydrocarbon, there being at least 0.1% by weight iodine, in the form of the complex, in the lubricant.

6. A lubricant comprising a hydrocarbon oil of lubricating viscosity containing dissolved therein a charge transfer COEII1P1X of iodine and a heterocyclic aromatic compound stable under the conditions it will be subjected to as a component of the lubricant, there being at least 0.1% by weight iodine, in the form of the complex, in the lubricant.

7. A lubricant comprising a hydrocarbon oil of lubricating viscosity containing dissolved therein a charge transfer complex of iodine and an amino-substituted aromatic hydrocarbon, there being at least 0.1% by Weight iodine, in the form of the complex, in the lubricant.

8. The process of lubricating two solid surfaces, at least one of which is at least by weight titanium, between which there is relative motion, which comprises maintaining a film of lubricant comprising a charge transfer complex of iodine and an aromatic compound stable under the conditions it will be subjected to as a component of the lubricant between the two surfaces, there being at least 0.1% by weight iodine, in the form of the complex, in the lubricant.

9. The process of claim 8 wherein the aromatic compound is an aromatic hydrocarbon.

10. The process of claim 8 wherein the aromatic cornpound is an alkyl-substituted aromatic hydrocarbon.

11. The process of claim 8 wherein the aromatic compound is a halogenated aromatic hydrocarbon.

12. The process of claim 8 wherein the aromatic compound is a hydrocarbonoxy-substituted aromatic hydrocarbon.

13. The process of claim 8 wherein the aromatic compound is a heterocyclic aromatic hydrocarbon.

14. The process of claim 8 wherein the aromatic compound is an amino-substituted aromatic hydrocarbon.

15. The process of claim 8 wherein the charge transfer complex is dissolved in a hydrocarbon oil of lubricating viscosity.

References Cited by the Examiner UNITED STATES PATENTS 3,184,409 5/ 1965 Furey 252- 33 FOREIGN PATENTS 761,362 11/1956 Great Britain.

OTHER REFERENCES DANIEL E. WYMAN, Primary Examiner.

JULIUS GREENWALD, Examiner.

R. E. HUTZ, E. W. GOLDSTEIN, P. P. GARVIN,

Assistant Examiners. 

7. A LUBRICANT COMPRISING A HYDROCARBON OIL OF LUBRICATING VISCOSITY CONTAINING DISSOLVED THEREIN A CHARGE TRANSFER COMPLEX OF IODINE AND AN AMINO-SUBSTITUTED AROMATIC HYDROCARBON, THERE BEING AT LEAST 0.1% BY WEIGHT IODINE, IN THE FORM OF THE COMPLEX, IN THE LUBRICANT. 